Shrinkage in multispan concrete bridge

1) Shrinkage and creep primary - these are imaginary forces which produce an equivalent elastic length change/curvature to the time dependent effects, is that right? Hence we do not consider them at ULS.
2) For shrinkage, Midas takes the notional size h as the only geometric input for a beam element. This is defined as a property of the material, which is a little counter intuitive. If we use a composite section for construction stage analysis, we can enter another h for each part of the section - does this override the notional size in the material definition?

3) The shrinkage secondary My in the model is enormous for the precast beams. long term construction stage - 2760 kNm. This is a similar magnitude to the dead load bending which intuitively seems completely wrong. Similarly the reactions at the base of the piers, which are up to 1460 kN. Please could you advise if it is correct? And if not, have we defined a model property incorrectly, or would this force actually be relieved by shrinkage cracking in the real structure? Or by the casting sequence of the top slab allowing for autogenous shrinkage before the next pour.

4) Similarly to thermal, the stiffness of restraint must have a big effect on the size of the shrinkage forces. Do we need to account for this flexibility somehow - eg the bearings used on the structure will not be rigid against uplift.

Answer: Yes, Creep and shrinkage are imaginary forces that produce equivalent elastic length change to time dependent effects. So, we need not to consider them at ULS combinations.

Answer: As shrinkage strain depend on the notional size of section hence, it is defined in shrinkage tab but generally, notional size value is generally updated using the properties>Time dependent properties>Change Property tab. Using this tab, software will auto-calculate the notional size of the selected section and shrinkage strains are calculated using this updated notional size. 

Moreover, the value defined in composite section for construction stage analysis will override the notional size defined earlier.

Hi,

I have a further question. Why should shrinkage not be considered on the transverse members? concrete shrinkage is a 3D effect so will cause strains in both directions of the slab plane. Do the dummy members not need to consider this? Similarly the diaphragm will be affected. As one side of the deck is released at the plinth members to simulate guided/free bearings, there should be no unusual forces against the rigid links?

Answer: